Interpretive Summary: Experiments were conducted to examine the influence of water hardness on the ability of water to rinse bacteria from the skin of processed broiler chickens. Distilled water was used as an example of soft water, and very hard artificial water was prepared by adding calcium and magnesium to distilled water. Moderately hard water was prepared by combining 1 part very hard with 1 part distilled water. Skin samples from processed chicken carcasses were rinsed for 5 consecutive times in fresh of portions of soft, moderately hard, or very hard water. After rinsing, skin was examined to determine how many bacteria could be recovered from the skin. Results indicated that fewer bacteria that are normally found in the intestinal tract of live chickens and fewer bacteria that cause spoilage of fresh chicken meat were recovered from skin samples rinsed in soft water than from skin rinsed in moderately hard or very hard water. Skin samples were also rinsed in very hard water that had been chemically softened by dissolving potassium citrate in the water. Results indicated that the chemically softened hard water was also more effective in rinsing bacteria from the skin than hard water. Findings from these experiments show that reducing water hardness can increase the ability of water rinses to remove some bacteria from processed chicken meat. These experiments indicate that poultry processors should monitor water hardness in their facilities, and that processors may be able to reduce bacterial contamination of chicken by reducing the hardness of water used in poultry processing operations.

Technical Abstract:
The effect of water hardness on the ability of water to rinse bacteria from the skin of processed broiler chickens was examined. Artificial hard water with a total hardness of 200 ppm (very hard water) was prepared by dissolving calcium chloride (CaCl2) and magnesium chloride hexahydrate (MgCl2 •6H2O) in distilled water, and water with a total hardness of 100 ppm (moderately hard water) was prepared by diluting 1 part very hard with 1 part distilled (soft) water. Five consecutive rinses of skin in fresh aliquots of soft, moderately hard, or very hard water were performed, and then samples were stomached in a solution of 0.01M potassium phosphate buffer with 0.025% ethylenediaminetetraacetic acid (EDTA) to recover bacteria remaining on the skin. Bacteria in stomached rinsates were enumerated on Plate Count (PC), Levine Eosine Methylene Blue (EMB), Campylobacter (CA), Pseudomonas (PS), and Staphylococci (ST) Agars. Results indicated that significantly (P < 0.05) fewer bacteria were recovered on CA and PS Agars from skin rinsed in soft water than from skin rinsed in moderately or very hard water, and significantly fewer bacteria were recovered on EMB Agar from skin rinsed in soft water than from skin rinsed in very hard water. Skin was also rinsed in very hard water that had been chemically softened by adding 0, 1.0, 2.5, or 5.0% potassium citrate. Results indicated that significantly (P < 0.05) fewer bacteria were recovered on EMB and CA Agars from skin rinsed in very hard water softened with 5.0% citrate than from skin rinsed in water with 0, 1.0, or 2.5% citrate added. Water hardness had no effect on the number of bacteria recovered on ST or PC Agars, however. In vitro tests indicated that citrate was not bactericidal towards Escherichia coli, Campylobacter jejuni, or Staphylococcus simulans isolates recovered from broiler skin. Findings from these experiments indicate that reducing water hardness can increase the ability of water rinses to remove bacteria normally found in the water layer covering the surface of the skin, but not bacteria embedded in fats and proteins secreted by the skin. Since most pathogenic and spoilage bacteria reside in the water layer on the surface of processed poultry meat, poultry processors may be able to reduce the number of these bacteria on processed poultry by monitoring and controlling the hardness of processing water.